(Newser)
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Federal experts investigating the Minneapolis bridge disaster have identified a structural flaw that may have led to the collapse, reports the New York Times. Investigators suspect that steel gusset plates used to connect the girders weren't strong enough to support the bridge right from the start. Federal authorities immediately warned states to be careful to calculate added weight when assigning construction crews to work on bridges.

A full crew was working on the Minnesota bridge when it buckled last week. The 5-foot-square plates are used in many bridges across the nation; failure to identify the flaw earlier could indicate a problem with the federal inspection program. Minnesota engineers, however, are baffled because the plates had raised no concerns through decades of inspections.